Cylindrical electrode system for focusing and deflecting an electron beam

ABSTRACT

An electron optical system permitting both focusing and deflection of an electron beam utilizes a plurality of sets of electrodes, each set of electrodes comprising two pairs of conductive coatings distributed according to a predetermined pattern and formed coaxially with the path of the undeflected electron beam emerging from a cathode. The electrodes of each set are formed of substantially the same radius of curvature, and the sets are aligned, one ahead of the other, along the path of the undeflected electron beam.

Waited States Patent 1191 Roussin [54] CYLINDETCAL ELECTRODE SYSTEM FUR FOCUSING AND DEFLECTING AN ELECTRON BEAM [75] Inventor: Alfred G; Roussin, Syracuse, N.Y.

[7 3] Assignee: General Electric Company,

Syracuse, N.Y.

[22] Filed: Apr. 19,1971

[21] Appl. No.1 135,240

[52] U.S.Cl. ..3l5/16, 315/17, 315/31 R,

. 313/78 [51] int. Cl ..H0lj 29/56 [58] Field of Search ..315/l5,l6, 17,18, 315/31 R, 23;3l3/78;335/210 [56] References Cited UNITED STATES PATENTS Llewellyn ..3 1 5/31 R Van Overbeek ..1 ..3l5/l8 1 1 May1,1973

2,899,597 8/1959 Kompfner ..3l5/l8 X 3,373,310 3/1968 Worcester ..3l5/18 3,397,341 8/1968 Guyot et al ..3l5/l7 Primary ExaminerCarl D. Quarforth Assistant Examiner-P. A. Nelson I Att0rneyMarvin Snyder, W. Joseph Shanley, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman [57] ABSTRACT An electron optical system permitting both focusing and deflection of an electron beam utilizes a plurality of sets of electrodes, each set of electrodes comprising two pairs of conductive coatings distributed according to a predetermined pattern and formed coaxially with the path of the undeflected electron beam emerging from a cathode. The electrodes of each set are formed of substantially the same radius of curvature, and the sets are aligned, one ahead of the other, along the path of the undeflected electron beam.

10 Claims, 8 Drawing Figures PATENTED MAY 1 I973 SHEET 1 OF 3 ELECT RON PAT H I k4. ZOFPQMJ w mw R me ,5 mm R m F F L A I BY J 360 HIS ATTORN Y PATENTEU W 1 1973 3. 731 1 36 SHEET 3 BF 3 VERT. HOR. VERT. HOR.

FIG.6

ELECTRON PATH ELECTRN PATH INVENTORZ ALFRED G. ROUSSIN,

ms ATTO NEY.

CYLHNDRICAL ELECTRODE SYSTEM FOR FOCUSING AND DEFLECTING AN ELECTRON BEAM INTRODUCTION This invention relates to electron beam focusing and deflection electrodes, and more particularly to an electron beam focusing and deflection electrode system of high deflection sensitivity capable, without correction voltages, of providing flat image fields.

In electrostatic electron beam focusing and deflection systems, it is desirable to achieve a high degree of deflection sensitivity without necessitating insertion of additional voltages to assure production of flat image fields. Additionally, if electron beam focusing and deflection signals are supplied to apparatus situated close to the region of the tube in which the electron beam is generated, the apparatus within the tube is greatly simplified. Moreover, if the electron beam is situated within a light valve so as to deform a film of light modulating fluid in accordance with information to be optically displayed on a remote screen, and light is directed through the tube so as to fall upon, and be modulated by, the film of light modulating fluid, it is desirable to minimize introduction of opaque surfaces into the beam of light so as to maximize optical efficiency of the light valve.

One type of focusing and deflection electrodes which has been employed in light valves is described and claimed in W. E. Glenn, Jr., U.S. Pat. 3,320,468, issued May 16, 1967, and assigned to the instant assignee. The electrodes of the Glenn patent are of the box" type; that is, they comprise opposed, flat, parallel deflection plates. While electrodes of this type are entirely satisfactory in operation, there are additional advantages to be gained if, instead of box type electrodes, the focus and deflection electrodes comprise conductive coatings distributed according to a predetermined pattern and formed coaxially with the path of. an undeflected electron beam emerging from a cathode. One such advantage is that the system is capable of providing flat image field planes simply by applying the horizontal and vertical rate voltage waveforms to corresponding horizontal and vertical deflection electrode pairs in the beam entrance section of an Einzel lens configuration formed by the electrodes. Image plane tilt correction may be obtained automatically by controlling deflection sweep unbalance from a true push-pull condition. Moreover, excessively high degrees of dimensional accuracy are not required in the lens configuration and the system readily lends itself to low-cost mass production in that the cylinder on which the electrodes are formed may also serve as the envelope for the vacuum tube in which they are contained. This is especially desirable since these electrodes do not add any substantial opaque surfaces in the beam of light. Another advantage is that, for any given electron lens throat cross-sectional area and a given electron beam object-to-image distance, electron beam deflection sensitivity is greatly increased. Finally, because the conductive surfaces in each set of electrodes are everywhere equidistant from, and surround, the undeflected electron beam axis, the beam is less susceptible to aberrations of its path resulting from stray fields.

Accordingly, one object of the invention is to provide electron beam focus and deflection electrodes of cylindrically curved configuration, wherein at least one set of electrodes enables performance of both focus and deflection functions.

Another object is to provide a lens for an electron beam capable of producing flat image field planes when horizontal and vertical sweep voltage waveforms are apportioned, at relatively low amplitude, to corresponding horizontal and vertical deflection electrode pairs in the beam entrance section of the lens.

Another object is to provide electron beam focus and deflection electrodes which do not require a high degree of dimensional accuracy for successful operation.

Another object is to provide an electron beam focus and deflection system of high deflection sensitivity, wherein susceptibility of the electron beam to aberrations of its path is minimized.

Another object is to provide a coincident set of flat image planes for the vertical and horizontal paths swept by a focused electron beam which remains undistorted in its vertical and horizontal dimensions.

Briefly, in accordance with a preferred embodiment of the invention, a system of electrodes for both focusing and deflecting an electron beam comprises at least first and second sets of cylindrically curved electrodes separately spaced along a common axis coinciding with the path of the undeflected electron beam emerging from a cathode so that the second set of electrodes is situated closer to the cathode than the first set. Each set of electrodes comprises four separate electrodes arranged about the common axis with the entire surface of each electrode being situated substantially equidistantly from the common axis and with the surfaces of each pair of adjacent electrodes being electrically insulated from each other and their opposed edges interleaved. The centroid of each electrode in each set respectively, is situated substantially at the junction of adjacent quadrants, respectively, on the circumference of a circle centered about the axis and defined by the electrode surfaces in each set, respectively. In each set of electrodes, a first electrical potential is applied across one pair of electrodes having diametrically-opposed centroids and a second electrical potential is coupled across the remaining pair of electrodes, with the second set of electrodes receiving predeflection potentials and the first set of electrodes receiving vertical and horizontal focus, vertical and horizontal raster positioning, and vertical and horizontal deflection potentials.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. I is an isometric view of one embodiment of the invention;

FIG. 2 is a diagram showing, in schematic form, electrodes employed in the embodiment of FIG. 1, electrical connections thereto, and other electrodes involved in producing and controlling an electron beam;

FIG. 3 is an end view of the embodiment of FIG. 1, showing locations at which electrical connections are made to the electrodes;

FIG. 4 is a plan view of one set of electrodes employed in the embodiment of FIG. 1, shown unrolled as a flat surface in order to illustrate the electrode pattern;

FIG. 5 is a plan view of a set of electrodes of another configuration, shown unrolled as a flat surface in order to illustrate the electrode pattern;

FIG. 6 is a plan view of a set of electrodes of yet another configuration, shown unrolled as a flat surface in order to view the electrode pattern;

FIG. 7 is an isometric view of another embodiment of the invention; and

FIG. 3 is an isometric view of a portion of still another embodiment of the invention.

DESCRIPTION OF TYPICAL EMBODIMENTS The concept of employing an electrostatic analog of an electromagnetic deflection yoke, known as a Deflectron, in order to deflect an electron beam in each of two, mutually perpendicular directions is described starting on page 667 of Fink, Television Engineering Handbook, first edition (McGraw-Hill, 1957). The Deflectron conventionally permits the electron beam to be deflected in both directions with equal deflection sensitivity and a common center of deflection. Heretofore, however, Deflectrons have been considered incapable of also focusing the electron beam. In the present invention, Deflectrons are employed for the purpose of both focusing and deflecting the electron beam.

The apparatus of FIG. ll comprises first and second sections 10 and M, respectively, of patterned, cylindrical conducting means generally defining a hollow cylindrical shape, with each section made up of electron beam modifying means. Cylindrical conducting means 10 comprises horizontal focus and deflection electrodes 13 and 14 having their centroids situated at diametrically opposed regions of the cylindrical configuration, and vertical focus and deflection electrodes 15 and 16 having their centroids situated at diametrically opposed regions of the cylindrical configuration. The patterns of each of horizontal electrodes 13 and 14 are identical, as are the patterns of each of vertical electrodes 15 and 16. Opposed edges of adjacent electrodes are interleaved, leaving an electrically insulating region 17 separating them from each other. Similarly, cylindrical conducting means 11 comprises horizontal deflection electrodes 18 and 19 having their centroids situated at diametrically opposed regions of the cylindrical configuration, and vertical focus and deflection electrodes, only one of which, 20, is visible, situated at diametrically opposed regions of the cylindrical configuration. The patterns of each of horizontal electrodes H8 and 19 are identical, as are the patterns of each of the vertical electrodes of cylindrical conducting means 11. Opposed edges of adjacent electrodes in section 11 are interleaved, leaving electrically insulating region 117 separating adjacent electrodes from each other. In addition, insulating region 17 also separates the electrodes of cylindrical conducting means 10 from the electrodes of cylindrical conducting means 11. The centroids of electrodes 15 and 20 are situated along an imaginary line 9, shown dotted. Thus, in each of cylindrical conducting means 10 and 11, the centroid of each electrode is situated substantially at the junction of adjacent quadrants on the circumference of a circle centered about, and orthogonal to, the longitudinal axis of the cylindrical configuration.

Although supporting means for the electrodes of cylindrical conducting means 10 and 11 are not shown, electrodes of this type may be readily formed by deposition of a thin layer of a conductive material, as by spraying silver paint, evaporating metal such as aluminum, electrodepositing a metal such as nickel or titanium, etc., upon the inner surface of a drawn glass cylinder, such as the envelope of a light valve tube. The glass, moreover, serves electrically to insulate the electrodes from each other if regions 17 are masked during formation of the electrodes to avoid deposition of any conductive material on regions 17. Electrical connection to each electrode from outside the tube may be made by employing a separate connector for each electrode to function as an electrical feedthrough imbedded in the glass and passing entirely through the thickness of the glass wall.

It should be noted that cylindrical conducting means 11 is shorter in length, measured along the path of an electron beam passing therethrough in the direction indicated, than conducting means 10. With cylindrical conducting means 10 operated at a DC potential sufficiently negative with respect to the DC potential on cylindrical conducting means ll 1 so as to focus the electron beam onto an electron beam target E2, the degree of focusing or demagnification of the electron beam is controlled in accordance with the relative lengths of cylindrical conducting means 10 to cylindrical conducting means lll, as measured along the electron path. The relatively negative potential on cylindrical conducting means 10 increases the electron beam transit time within the region enclosed by electrodes 13, 14, 15 and 16, resulting in high deflection sensitivity. The desired electrostatic deflection voltage waveforms are supplied to the electrodes of both of cylindrical conducting means 10 and 11.

FIG. 2 is a schematic illustration of the cylindrical conducting means of FIG. ll, showing typical electrical connections thereto when the cylindrical conducting means are employed in a light valve of the type described, for example, in W. B. Good et al. U.S. Pat. No. 3,385,925, issued May 28, 1968 and assigned to the instant assignee. Thus, horizontal focus and deflection electrodes 13 and 14 receive DC focusing and raster positioning voltages through resistances 2S and 26, respectively. Similarly, vertical focus and deflection electrodes 15 and 16 receive DC focusing the raster positioning voltages through resistances 27 and 28, respectively. Positive and negative horizontal sweep signals are furnished through resistances 30 and 31, respectively, in series with coupling capacitances 32 and 33, respectively, to horizontal focus and deflection electrodes M and 13, respectively. Similarly, positive and negative vertical sweep signals are furnished through resistances 34 and 35, respectively, in series with coupling capacitances 36 and 37, respectively, to vertical focus and deflection electrodes 15 and 16, respectively. Red and blue radio frequency signals, comprising the sum or red and blue carriers amplitudemodulated with red and blue video signals, respectively, are furnished to horizontal focus and deflection electrodes 13 and 14, respectively, through coupling capacitances 38 and 39, respectively, in series with coupling capacitances 33 and 32, respectively. Relative polarities of the red and blue RF signals are as marked at the inputs to capacitances 38 and 39. In similar fashion, green carriers, amplitude-modulated with the video signal representing green information, are furnished through coupling capacitances 45 and 46, respectively, in series with coupling capacitances 36 and 37, respectively, to vertical focus and deflection electrodes 15 and 16, respectively. Vertical focus and deflection electrode 16 is illustrated through a cutaway portion of vertical focus and deflection electrode 15.

In similar fashion, the positive and negative horizontal sweep voltages are applied to horizontal deflection electrodes 19 and 18, respectively, through capacitances 50 and 51, respectively, while the positive and negative vertical sweep voltages are applied to vertical deflection electrodes 20 and 21, respectively, through capacitances 52 and 53, respectively. Bias voltages are applied to electrodes 18, 19, 20 and 21 through resistances 54, 55, 56 and 57, respectively, to statically center the beam along the longitudinal axis of cylinders and 11. Vertical deflection electrode 21 is illustrated through a cutaway portion of vertical deflection electrode 20.

In order to illustrate the relative positions of cylindrical conducting means 10 and 11 in a light valve, additional electron beam controlling apparatus is schematically depicted. This apparatus includes a cathode 40, comprising the source of electrons for the light valve, a grid 41 for controlling intensity of the electron beam, an anode 42, containing an electron optical object aperture 47 therein, for accelerating electrons emitted by cathode 40 and passing grid 41, and an electrode 43 comprising conductive optical Schlieren input bars to form an electron lens termination plane for the electron beam prior to its entering the region enclosed by cylindrical conducting means 10 and 11. Typically, cathode 40 is operated at ground potential, grid 41 at -120 to -200 volts, anode 42 at +8,000 volts, and electrode 43 at +8,000 volts. Target 12 is typically operated at +8,000 volts. Typically, volts, and typical AC voltages thereon voltages on the electrodes of cylindrical conducting means 10 are in the range of from approximately 30 volts to +300 volts, and typical AC voltage thereon are approximately 1,200 volts peak-to-peak. Typical DC voltages applied to the electrodes of cylindrical conducting means 11 may range from +7,800 to +8,200 volts, and typical AC voltages applied thereto are on the order of 300 volts peak-toeak. p FIG. 3 is an end view of the apparatus shown in FIG. 1, as viewed from the end at which the electron beam emerges, illustrating relative locations of electrodes 13, 14, and 17, and insulating regions 17, of cylindrical conducting means 10. Electrodes 13, 14, 15 and 16 are illustrated without any supports other than leads 24, in

which case insulating regions 17 are preferably com-.

prised of a solid insulating material joining the electrodes so as to form a unitary, hollow cylinder; however, as previously mentioned, the electrodes may be deposited or otherwise formed on the inside surface of the envelope ofa glass tube comprising the envelope of a light valve, in which case insulating regions 17 may simply comprise open spacing separating the electrodes from each other.

FIG. 4 is an illustration of cylindrical conducting means 10 of FIG. 1, shown in a flat, or unrolled, configuration. The relative locations of electrodes 13, 14, 15 and 16 are illustrated with respect to insulating regions 17. Regions 17 merely comprise open spacings to achieve electrical insulation of electrodes from each other in this embodiment. The polar coordinate angle designations of 0, and 360 are added for ease in relating the unrolled configuration of FIG. 4 to the cylindrical configuration illustrated in FIG. 1, it being understood that the configuration of FIG. 4 is rolled so that the 0 and 360 lines coincide. With the path of electrons following the direction indicated, cylindrical conducting means 11, if unrolled, would properly be situated in FIG. 4 below conducting configuration 10.

Operation of the system of the instant invention may be readily understood by reference to FIG. 2. The portion of electrons emitted from cathode 40 and which is accelerated by anode 42 is determined by the amplitude of negative voltage on grid 41 so as to control intensity of the electron beam. Electrons passing through aperture 47 in anode 42 continueto travel toward electrode 43. The beam cross section size and shape are determined by aperture 47 in anode 42, and aperture 47 serves as the electron object size from which electrons travel past electrode 43 through the regions enclosed by cylindrical conducting means 10 and 11 toward electron receiving surface 12. The electron beam, in its undeflected path, passes along the common longitudinal axis of cylindrical conducting means 10 and 11. To provide the best balance between spot demagniflcation and size of the electron beam deflection angle, both focusing and deflection functions are combined in cylindrical conducting means 10. The horizontal and vertical sweep voltages typically comprise voltages of the periodicity normally used in television deflection circuits. Horizontal sweep voltage is applied to electrodes 13 and 14 of cylindrical conducting means 10 to provide the main horizontal deflection, and also to electrodes 18 and 19 of cylindrical conducting means 11 to provide a predeflection,-or deflection of the electron beam before it enters the focusing field established by the potential difference extant between cylindrical conducting means 10 and 11. Similarly, vertical deflection voltage is applied to electrodes 15 and 16 of cylindrical conducting means 10 and also to predeflection electrodes 20 and 21 of cylindrical conducting means 1 1.

Presence of deflection voltages on the electrodes of cylindrical conducting means 10 distorts the focusing field by moving the center of focus of the focusing field. In order to minimize or eliminate the effect of these dynamic changes in the focusing field, the electron beam is given a predeflection; that is, the electron beam, before entering the focusing field, is deflected in the same direction as the direction of deflection produced by the electrodes of cylindrical conducting means 10 and by an amount which tends to introduce the beam into the focusing field at the dynamic center of focus, which is the center of focus extant when the electric fields are at any instantaneous configuration and amplitude. The amount of predeflection of the' electron beam is preferably determined by the relative length, as measured along the longitudinal axis, of the electrodes in cylindrical conducting means to the electrodes in cylindrical conducting means 11. Conveniently, the relative lengths of cylindrical conducting means 10 and 11 may be chosen so that the same deflection voltages may be applied to corresponding electrodes of cylindrical conducting means 10 and 11, in which case the degree of focusing or demagnification is determined by the relative lengths of cylindrical conducting means llt) and ill.

The reason for efficient electron beam deflection by employment of Deflectrons is described in detail in Fink, Television Engineering Handbook, first edition (McGraw-Hill, 1957), pages 6-67 through 6-70. Moreover, because cylindrical conducting means It) is operated at more negative potential than cylindrical conducting means 11, electron beam transit time within the region enclosed by cylindrical conducting means W is increased. This results in a high degree of deflection sensitivity inasmuch as there is sufficient time for electrons, under the influence of the deflecting electric fields, to be deflected by a significant amount away from the longitudinal axis of cylindrical conducting means it). At the same time, the cylindrical conducting means acts as an electrostatic shield along its length, minimizing aberrations in the electron beam path caused by external electric fields.

The desired electrostatic focus voltages and deflection waveforms are supplied through appropriate circuitry to the electrodes of cylindrical conducting means it) and 11. Thus, focus voltages are supplied through current-limiting resistance means such as resistances 25, 26, 2'7 and 28 to electrodes 13, I4, 15 and 16, respectively, of cylindrical conducting means 10, so that only the potentials on these electrodes are employed to control focusing of the electron beam. The modulated RF signals are combined with the appropriate horizontal or vertical sweep signal through R- C circuits such as capacitance 38 and resistance 31, capacitance 39 and resistance 30, capacitance 45 and resistance 34, and capacitance 46 and resistance 35, and, in turn, are combined with theDC focusing voltages through capacitance 33 and resistances 25 capacitance 32 and resistance 26, capacitance 36 and resistance 27, and capacitance 37 and resistance 28, respectively, for application to electrodes 13, 14, 15 and 16, respectively, so as to control electron beam deflection resulting from sweep and modulating signals. In this fashion, the voltage on each of the electrodes of cylindrical conducting means lit) varies in accordance with focus voltage, sweep voltage and amplitude modulated primary color voltage. In similar fashion, appropriate sweep voltages are applied to the electrodes of cylindrical conducting means 1 l in order to achieve the electron beam predeflection, previously described, resulting solely from sweep signals.

FIG. 5 illustrates, in a flat or unrolled condition, an alternate configuration for either or both of cylindrical conducting means 10 and ill of FIG. 1. The electrodes, in this configuration, are designed with boundaries on the surface of the cylinder that are of sinusoidal shape as viewed along the longitudinal axis of the cylinder. In addition, FIG. 5, shows that the number of peaks and troughs in the edges of the electrodes is not restricted to any particular number such as the number shown in FIG. 4. Among the reasons for changing the shape of the boundaries of the electrodes along the surface of the cylinder, or for changing the numbers of peaks and troughs in these boundaries, are to obtain particular vertical and horizontal deflection centers and to minimize any differences in vertical and horizontal electron lens focal lengths and principal electron beam focal planes. A deflection center may be defined herein as the intersection of the forwardly-projected electron path prior to deflection and the rearwardly-projected electron path in the field-free space after deflection, as well known in the art.

FIG. 6 illustrates, in a flat or unrolled condition, a third configuration of electrodes which may comprise yet another alternate configuration for cylindrical conducting means 10 of FIG. ll. In this configuration, electrodes l3, l4, l5 and 16 all remain insulated from each other, but each electrode is continuous along the entire length of cylindrical conducting means 10. The electrodes receive horizontal and vertical deflection signals, as indicated, in a manner similar to that shown in the apparatus of FIG. 2. As indicated on page 6-69 of the aforementioned publication by Fink, each of electrodes 13, 114, 15 and I6 is bounded by two halfwaves of a sine, each extending over 180 of the perimeter of the cylinder, and each boundary of an electrode is offset by 90 from the corresponding boundary of the preceding one. Insulating regions 17 separate each of the electrodes from each other. The electrode configuration of FIG. 6 can provide particularly wide angle deflection of the electron beam.

FIG. 7 illustrates an Einzel lens configuration incorporating the instant invention. An Einzel lens, as is well-known in the art, includes three lens electrodes aligned along a common axis, with the two external electrodes being operated at a common DC potential and the center electrode being operated at some other, more negative, potential. Einzel lens systems are commonly used to focus an electron beam. The Einzel lens configuration of FIG. 7 comprises first, second and third sections 60, 61, and 62, respectively, of patterned, cylindrical conducting means comprising electrostatic deflection electrodes for an electron beam. Cylindrical conducting means 60 comprises horizontal focus and deflection electrodes 63 and 64 situated at diametrically opposed regions of the cylindrical configuration, and vertical focus and deflection electrodes 65 and 66 situated at diametrically opposed regions of the cylindrical configuration spaced 90 apart from electrodes 63 and 64. The patterns of each of horizontal electrodes 63 and 64 are identical, as are the patterns of each of vertical electrodes 65 and 66. Opposed edges of adjacent electrodes are interleaved, leaving an electrically insulating region 67 separating adjacent electrodes from each other.

Cylindrical conducting means 61 similarly comprises horizontal focus and deflection electrodes 68 and 70 situated at diametrically opposed regions of the cylindrical configuration, and. vertical focus and deflection electrodes 72 (not visible) and 71 situated at diametrically opposed regions of the cylindrical configuration spaced apart from electrodes 68 and 70. The pat terns of each of horizontal electrodes 68 and 70 are identical, as are the patterns of each of vertical electrodes 7K and 72. Opposed edges of adjacent electrodes are interleaved, leaving electrically insulating region 67 separating adjacent electrodes from each other.

Cylindrical conducting means 62 comprises horizontal deflection electrodes 73 and 74 situated at diametrically opposed regions of the cylindrical configuration, and vertical deflection electrodes 76 (not visible) and 75 situated at diametrically opposed regions of the cylindrical configuration spaced 90 apart from electrodes 73 and 74. The patterns of each of horizontal electrodes 73 and 74 are identical, as are the patterns of each of vertical electrodes 75 and 76. Opposed edges of adjacent electrodes are interleaved, leaving electrically insulating region 67 separating adjacent electrodes from each other. Region 67 also separates the electrodes of set 61 from the electrodes of each of sets 60 and 62. I

In operation, anode potential is applied to each electrode of sets 60 and 62, and a negative, focusing voltage below anode potential is applied to each electrode of set 61. In addition, although not shown for simplicity sweep voltages and radio frequency voltages are applied to the electrodes of sets 61 and 60 in the same manner as they are applied to the electrodes of set 10 as shown in FIG. 2. Sweep voltages, similarly not shown for simplicity are also applied to the electrodes of set 62 in the same manner as they are applied to the electrodes of set 11 as shown in FIG. 2. Thus, beam deflection resulting from sweep and modulation voltages occurs within the regions enclosed by the electrodes of sets 61 and 60, and beam deflection resulting from sweep voltages only occurs within the region enclosed by the electrodes of set 62. The focusing function is performed by the electric field established between the electrodes of set 61 and the electrodes of set 62, as well as by the electric field established between the electrodes of set 61 and the electrodes of set 60. Because the focusing and deflecting action of the electrodes of set 61 causes the lens to actas though tilted, which may result in a distortion of the image produced by the beam, the predeflection action introduced by the electrodes of set 62 directs the electron beam toward a location within the region enclosed by the electrodes of set 61 so as to counteract the lens tilt and assure production of a flat image which is everywhere in focus. As an alternative to the configuration of FIG. 7, the electrodes of set 60 may be combined into a unitary cylindrical structure in the manner illustrated by the fragmentary diagram of FIG. 8 inasmuch as such structure need only produce an electric field that interacts with the field produced by set 61 to accomplish the focusing action. 7

The foregoing describes electron beam focus and deflection electrodes of cylindrical configuration wherein at least one set of electrodes performs both focus and deflection functions. The electrodes are capable of providing flat image field planes when vertical and horizontal sweep voltage waveforms are apportioned, at a relatively low amplitude, to corresponding vertical and horizontal deflection electrode pairs in the beam entrance section of the lens. The electron beam focus and deflection electrodes do not require a high degree of dimensional accuracy, and susceptibility of the electron beam to aberrations of its path is minimized. Thus, the apparatus of the invention provides the advantages resulting from the desirable deflection characteristics of the Deflectron with the ability to focus the electron beam, assuring production of a flat image plane which is everywhere in focus.

While only certain preferred features of the invention have been shown by way of illustration, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

I claim:

ll. Apparatus for focusing and deflecting an electron beam comprising:

a first set of cylindrically curved electrodes spaced along an axis coinciding with the path of the undeflected electron beam emerging from a cathode,

said first set comprising four electrodes arranged about said axis so that the entire surface of each of said electrodes of said first set is situated substantially equidistantly from said axis, the surfaces of each pair of adjacent electrodes being electrically insulated from each other and their opposed edges being interleaved;

a second set of cylindrically curved electrodes spaced along said axis at a greater distance from said cathode than said first set, said second set comprising four electrodes arranged about said axis so that the entire surface of each of said electrodes of said second set is situated substantially equidistantly from said axis, the surfaces of each pair of adjacent electrodes in said second set being electrically insulated from each other and their opposed edges being interleaved,

each electrode in each set having its centroid situated, respectively, substantially at the junction of adjacent quadrants, respectively, on the circumference of a circle centered about said axis and defined by the electrode surfaces in said each set; and

means coupled to the electrodes of said first and second sets for maintaining the electrodes of said second set at a relatively negative. potential with respect to the electrodes of said first set in order to establish an electric field between said first and second sets for focusing said electron beam and to provide said second set with a high degree of deflection sensitivity by slowing the velocity of electrons arriving in the vicinity of said second set.

2. The apparatus of claim 1 including means coupled to each of the electrodes of said first set for furnishing deflection voltages thereto, and means coupled to each of the electrodes of said second set for furnishing deflection voltages thereto.

3. The apparatus of claim 1 including a third set of cylindrically curved electrodes centered about said axis and spaced along said axis at a greater distance from said cathode than said second set, and means coupled to the electrodes of said third set for maintaining said third set at a relatively positive potential with respect to the electrodes of said second set in order to establish an electric field between said second and third sets for additionally focusing said electron beam.

4. The apparatus of claim 3 wherein said third set of cylindrically curved electrodes defines a single, unitary surface surrounding said axis.

5. The apparatus of claim 3 wherein said third set of cylindrically curved electrodes comprises four electrodes arranged about said axis so that the entire surface of each of said electrodes of said third set is situated substantially equidistantly from said axis, the surfaces of each pair of adjacent electrodes in said third set being electrically insulated from each other and their opposed edges being interleaved, each electrode in said third set having its centroid situated, respectively, substantially at the junction of adjacent quadrants, respectively, on the circumference of a circle centered about said axis and defined by the electrode surfaces in said third set.

6. The apparatus of claim 3 including means coupled to each of the electrodes of said first set for furnishing deflection voltages thereto, means coupled to each of the electrodes of said second set for furnishing deflection voltages thereto, and means coupled to the third set of electrodes for furnishing deflection voltages thereto.

7. The apparatus of claim 4 including means coupled to each of the electrodes of said first set for furnishing deflection voltages thereto, and means coupled to each of the electrodes of said second set for furnishing deflection voltages thereto, the unitary surface of said third set being maintained relatively positive with respect to said second set.

8. The apparatus of claim 1 wherein said electrodes are formed upon the inner surface of a glass cylinder.

9. The apparatus of claim 3 wherein said electrodes are formed upon the inner surface of a glass cylinder.

10. The apparatus of claim 1 wherein the electrodes of said first set are of a first predetermined length and the electrodes of said second set are of a second predetermined length, said apparatus further including means coupled to each of the electrodes of said first and second sets for furnishing substantially equal deflection voltages to corresponding electrodes, respectively, of said first and second sets such that the degree of focusing is determined by the relative lengths of the electrodes of said first and second sets.

UNI D STATES I TATE NT OFFICE CERTIFICATE CORRECTION Patent No. 3,731,136 Dated May 1, 1973 Inventor) A1 fred G. Roussin i It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 53, cancel "focus and". Column 5, lines 44 to and 45 "volts, and typical AC voltages thereon" should read DC Column 7', line 44, "resistances" should-read resistance 1' Signed and sealed this 8th day of January 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer 1 Acting Commissioner of Patents FORM Po-1050 (10-69) I USCOMM-DC 60376-P69 I U.S. GOVERPAMENT PRINTING OFFICE 9G9 O-JGG-Sll.

UNITED STATES fiATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,731,136 Dated May 1, 1973 Inventor(s) Alfred 'G. Roussin It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 53, cancel "focus and". Column 5, lines 44 to and 45, "volts, and typical AC voltages thereon" should read DC Column 7, line 44, "resistances" should-read resistance 1 1 Signed and sealed this 8th day of January 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER C Attesting Officer Acting Commissioner of Patents y: 90.1050 (10-69) USCOMM-DC 60376-P69 V U.S GOVERNMENT PRINTING OFFICE: '99 l"331 I 

1. Apparatus for focusing and deflecting an electron beam comprising: a first set of cylindrically curved electrodes spaced along an axis coinciding with the path of the undeflected electron beam emerging from a cathode, said first set comprising four electrodes arranged about said axis so that the entire surface of each of said electrodes of said first set is situated substantially equidistantly from said axis, the surfaces of each pair of adjacent electrodes being electrically insulated from each other and their opposed edges being interleaved; a second set of cylindrically curved electrodes spaced along said axis at a greater distance from said cathode than said first set, said second set comprising four electrodes arranged about said axis so that the entire surface of each of said electrodes of said second set is situated substantially equidistantly from said axis, the surfaces of each pair of adjacent electrodes in said second set being electrically insulated from each other and their opposed edges being interleaved, each electrode in each set having its centroid situated, respectively, substantially at the junction of adjacent quadrants, respectively, on the circumference of a circle centered about said axis and defined by the electrode surfaces in said each set; and means coupled to the electrodes of said first and second sets for maintaining the electrodes of said second set at a relatively negative potential with respect to the electrodes of said first set in order to establish an electric field between said first and second sets for focusing said electron beam and to provide said second set with a high degree of deflection sensitivity by slowing the velocity of electrons arriving in the vicinity of said second set.
 2. The apparatus of claim 1 including means coupled to each of the electrodes of said first set for furnishing deflection voltages thereto, and means coupled to each of the electrodes of said second set for furnishing deflection voltages thereto.
 3. The apparatus of claim 1 including a third set of cylindrically curved electrodes centered about said axis and spaced along said axis at a greater distance from said cathode than said second set, and means coupled to the electrodes of said third set for maintaining said third set at a relatively positive potential with respect to the electrodes of said second set in order to establish an electric field between said second and third sets for additionally focusing said electron beam.
 4. The apparatus of claim 3 wherein said third set of cylindrically curved electrodes defines a single, unitary surface surrounding said axis.
 5. The apparatus of claim 3 wherein said third set of cylindrically curved electrodes comprises four electrodes arranged about said axis so that the entire surface of each of said electrodes of said third set is situated substantially equidistantly from said axis, the surfaces of each pair of adjacent electrodes in said third set being electrically insulated from each other and their opposed edges being interleaved, each electrode in said third set having its centroid situated, respectively, substantially at the junction of adjacent quadrants, respectively, on the circumference of a circle centered about said axis and defined by the electrode surfaces in said third set.
 6. The apparatus of claim 3 including means coupled to each of the electrodes of said first set for furnishing deflection voltages thereto, means coupled to each of the elecTrodes of said second set for furnishing deflection voltages thereto, and means coupled to the third set of electrodes for furnishing deflection voltages thereto.
 7. The apparatus of claim 4 including means coupled to each of the electrodes of said first set for furnishing deflection voltages thereto, and means coupled to each of the electrodes of said second set for furnishing deflection voltages thereto, the unitary surface of said third set being maintained relatively positive with respect to said second set.
 8. The apparatus of claim 1 wherein said electrodes are formed upon the inner surface of a glass cylinder.
 9. The apparatus of claim 3 wherein said electrodes are formed upon the inner surface of a glass cylinder.
 10. The apparatus of claim 1 wherein the electrodes of said first set are of a first predetermined length and the electrodes of said second set are of a second predetermined length, said apparatus further including means coupled to each of the electrodes of said first and second sets for furnishing substantially equal deflection voltages to corresponding electrodes, respectively, of said first and second sets such that the degree of focusing is determined by the relative lengths of the electrodes of said first and second sets. 